The present invention relates to a tape for TAB (Tape Automated Bonding) by which leads are formed by photolithography and the ends of these leads are bonded to corresponding bumps of a chip.
As an optimal method for integrating and mounting LSIs at a high density, a method called TAB (Tape Automated Bonding) in which all pads on a chip are bonded to terminals on a package at one time by using metal leads is used recently. In this method, leads are formed by photolithography for each frame of a film-like tape made of a polyimide film, and the ends of these leads are bonded to bumps formed on corresponding electrodes of a chip.
FIG. 10 is a perspective view schematically showing a bonding state between a chip and leads connected by this TAB method. Referring to FIG. 10, reference numeral 1 denotes a chip; 2, leads; and 3, outer leads as the terminal ends of the leads.
First, a formation region for the chip 1 is opened in a TAB tape which is made of a polyimide film, and on the upper surface of which an adhesive is coated. A copper foil or film is pasted on the upper surface of this TAB tape. A resist pattern corresponding to the shape of the leads 2 is formed on this copper foil by using the technique of photography. Thereafter, unnecessary portions of the copper foil are removed by using the resist pattern as a mask. The ends of the leads 2 are bonded in a one-to-one correspondence with a signal electrode SIG, a power supply electrode VCC, and a ground electrode VSS. Note that the outer leads 3 formed on the terminal ends of the leads 2 are connected to a substrate, such as a printed circuit board, or to inner leads of a lead frame through a process of, e.g., bonding.
Conventionally, however, the leads 2 are connected in a one-to-one correspondence with the electrodes of the chip 1. Therefore, if the degree of integration of the chip 1 is increased to increase the number of electrodes of the chip 1, the number of leads 2 also increases accordingly. This makes it very difficult to connect the leads to a substrate or a lead frame.